This CPU will be the successor or the current PIII and maybe even the Celeron. 

The speed of the one released is 1.13 & 1.2GHz , with faster PIII's coming soon. I expect Intel to keep PIII at speeds below the Pentium 4 since it would be silly to have Tualatin competing with their high-end Pentium 4 processors.

The main difference between the Tualatin and the 'old' version is mainly the manufacturing process (0.18 to 0.13 micron design), which enables Intel to continue to make PIII faster. The other differences are voltage, and the main one we are looking for is the performance aspect of the chip. Lets hope its good!  

If you want to upgrade, you'll have to change your mainboard, because this CPU requires a lower voltage setting. The good thing is that you won't have to upgrade your case or your power supply (if your using an ATX Case).

The price of the 1.2GHz is between the price for a 1.5 and a 1.7GHz Pentium 4 - around $405USD, or $800 AUSD. The price should soon go down soon.

This processor looks great, and sounds promising - its great to see the trusty Pentium III live on.